TBX20 regulates epithelial‑mesenchymal transition, maintains tumor stemness and immune factor expression, and promotes immune escape in lung cancer

T‑box transcription factor 20 (TBX20) serves a crucial regulatory role in the process of tumor occurrence. In lung cancer, the upregulation of TBX20 expression is positively associated with a poor prognosis; however, the specific underlying mechanism remains unclear. Therefore, in the present study, the expression of TBX20 in normal lung epithelial BEAS‑2B and cancer cells A549 was detected by quantitative PCR and western blot. Lung cancer cell lines with overexpression and interference of TBX20 were constructed. Cell proliferation was detected by Cell Counting Kit‑8, cell migration and invasion were detected by Transwell, and cell spheroid formation was assessed. The expression of EMT markers (E‑cadherin, N‑cadherin, vimentin), stemness markers (CD44, Sox2, Nanog), and immune factors (PD‑L1, IL‑6, CCL2) was detected by qPCR and WB. A subcutaneous lung cancer model in nude mice was established. After 4 weeks, the tumor volume was observed. The expression of E‑cadherin, N‑cadherin, vimentin, CD44, and PD‑L1 in tumor tissues was detected by IHC. The infiltration of immune cells (CD8+T, CD4+T, M1/M2 macrophages) was detected by flow cytometry. In vitro experiments revealed that the expression levels of TBX20 were increased in the A549 lung cancer cells compared with those in BEAS‑2B normal lung epithelial cells. In addition, cell viability, migration, invasion and spheroid formation capacity were greater in the A549 group than in the BEAS‑2B group. Compared with in the negative control (NC) group, the TBX20 overexpression plasmid (oe‑TBX20) group exhibited enhanced cell viability, migration, invasion and spheroid formation capacity. Furthermore, E‑cadherin expression was reduced, whereas N‑cadherin, vimentin, Sox2, CD44, Nanog, PD‑L1, IL‑6 and CCL2 expression levels were elevated. Notably, these changes were reversed in the TBX20 knockdown group. In vivo experiments revealed that compared with in the NC group, the oe‑TBX20 group had significantly increased tumor volume, decreased E‑cadherin levels, and elevated expression levels of TBX20, N‑cadherin, vimentin, CD44 and PD‑L1. Compared with NC group, the oe‑TBX20 group exhibited significantly lower infiltration of CD4+ T and CD8+ T cells and M1‑type macrophage, whereas that of M2‑type macrophages and regulatory T cells increased. Conversely, these indicators were reversed in the short hairpin RNA‑TBX20 group. In conclusion, TBX20 may induce epithelial‑mesenchymal transition and stem cell characteristics, enhance the malignant behavior of lung cancer cells, and upregulate PD‑L1 expression to promote immune escape.